For instance, Japanese Unexamined Patent Application Publication (Translation of PCT Application) (JP-T) No. 2013-509328 discloses a capless refueling system that is disposed at the end of a filler pipe and utilizes snap mounting of a valve assembly. It is to be noted that “capless” indicates that a fuel cap conventionally provided in the fill opening is not provided.
The valve assembly includes a lower main body and an upper cover. In the lower main body, a flapper valve is disposed that is urged by a spring to a seated state. In the upper cover, another flapper valve is disposed that is urged by a spring to a seated state.
There is a case where an emergency nozzle (refueling auxiliary device) is inserted into the fill opening provided at the end of the filler pipe for refueling. In this case, for instance, when the end of the filler pipe is provided with the capless refueling system presented by JP-T No. 2013-509328, fuel vapor may blow back through the fill opening to the outside when the emergency nozzle is inserted.
That is, when the flapper valve of the capless refueling system is pressed by the end of the emergency nozzle and is fully opened, a fuel path sealed in the filler pipe is changed from in a pressurized state to an atmospheric release state rapidly, and thus fuel vapor may blow back to the outside.